Self-priming centrifugal pump



H E. LA BOUR SELF PRIMING CENTRIFUGAL PUMPv March-15, 1938.

Filed May 294, 1933 6 Sheets-Sheet 1 ILP. UNH. HIIIIH y In venon- 562WZcmf? H. E. LA BOUR SELF 4 PRIMNG CENTR IFUGAL PUMP 6 Sheets-Sheet 2Filed May 29, 1.953

March 15, 1938. H. E. LA BOUR SELF PRIMING CENTRIFUGAL PUMP Filed May29. 1933 6 sheets-sheet 5 wm @u afffy il; f

March Vl5,` 1938. H, E, LA BQUR .2,110,883

SELF PRIMING CENTRIFUGAL PUMP Filed May 29. i953 6 Sheets-Sheet 4 H. E.LA BOUR SELF PRIMING CENTRIFUGAL PUMP Filed May 29. 1953 6Sheets--Sheet` 5 March 15, 1938. H; E. LA BOUR 2,110,833

SELF PRIMING CENTRIFUGAL PUMP Filed May 29, 1933 6 Sheets-Sheet 6 l mi luhmm /////////////////77 l nl Patented 15, 1938 z,11u,ss3 SELF-ramocEN'rmFUGAr. PUMP Harry EfLa Bour, Elkhart, Ina. Application May 29,1933, Seal No. 673,469

-i 'sa claims.. (cl. ros-11s) f My invention relates to pumps, and moreparticularly to self-priming centrifugal pumps of the type disclosed inmy United States Patent No. 1,518,236. 'I'his type of pump employs theprinciple of hydraulic balance in the auxiliary or4 priming throat. Bythe employment of this principle, the rate andV direction of ilow ofliquid in the auxiliary or priming passageway may be` automaticallydetermined by the iluid which is being drawn through the suction pipeinto the v pump casing. When the pump 'casing is being evacuated by thewithdrawal of air from the pump casing and the suction pipe, thedirection of flow of liquid in the auxiliary or priming passageway isinwardly, and when the pump is pumping liquid the direction of flow isoutwardly.

This application is a continuation in part oi' `my application, SerialNo. 629,617, iiled August 20, 1932.

Pumps of the aforesaid class employ a charge of liquid operating in aclosed cyclebetween pump runner and separator forv evacuating the pumpand suction line of air or other gas, and upon attaining a fullcomplement of liquid the pressureA developed in the auxiliary, orprimingthroat,is great enough to oppose return flow of liquid and'preferably to serve as an additional discharge throat. f Y

In passing through this cycle of operations, i. e., evacuation, of thepumpcasing by pumping gas to a point where the suction pipe will be lledwith liquid and pumping'of liquid begins, two important phases ofoperation are exhibited. Therst is the automatic compensation or controlof rate of liquid reentry for changes in head or pressure differenceavailable upon the auxiliary or priming passageway,` causing return iiowof priming liquid during gas pumping. The second is the automaticstopping or reversal ,of ow in the auxiliary or priming passageway. Inthis phase of operation not only may the return ow or recirculation bereduced or stopped, but in the full use of the principle the ow isactually reversed, thereby constituting the auxiliary or primingpassageway an additional discharge passageway which increases both thecapacity and the efliciency of the pump.

It is the chief object of the present invention to provide in aself-priming pump a structure and mode voi' operation which will employthe aforesaid principle to greater advantage than has heretoiore'becnpossible. Y

More specically, it is an object of the invention, to increase the gaspumping capacity of a given size of pump.

It is a further object of the invention to increase the gas pumpingefficiency of self-priming pumps.

It is ay further obJect to increase the vacuum Y attained by pumps ofthis general class. 5

It is a further object to produce' a given rate of gas evacuation with asmaller amount of priming water than has heretofore been possible. Thispermits reduction in the voiumeof the inlet trap. l0

It is a further object to enhance the inherent stability of operationonprming and of equalizing the work upon the throats, particularlyduring priming. f

It is a further object to shorten the time re- 1.5

' quired to evacuate thepump`casing and suction pipe.

The increases ingas pumping capacity and efficiency, with resultingreduction in time required forpriming, andl ability to vdraw highervacua, are secured, as will `be set forth in detail later, b?Yimprovement in the structure'and mode of operation whereby thecirculating liquid is employed in a more advantageous manner forentraining and discharging gas and by a novel utilization oi theprincipleiof compensation.

A further object of the 1nvention is to increase the liquid Dumpingcapacity of a given size of pump of thisgeneral class.

Y Another object of the invention is to improve 30 the pumpingefficiency of hydraulic pumps, particularly pumps of the self-primingclass.

The increases in capacity and efliciency during liquid pumping aresecured, as will be set forth in detail later, by improvement instructure and mode of operation, whereby the liquid is carried' througha small angular travel and discharged through a plurality of throatsoperating in parallel about the periphery of the pump, and whereby animproved' utilization of the action of reverse 40 flow in the lauxiliaryor priming passageways is secured.

A further object of the invention is to improve the efliciency andincrease the capacity for gas disentrainment or separation in pumps oithis character.

This object is attained, as will oe described more in detail hereafter:partly by the discharge of the mixture of gas and liquid in parallelfrom a number of throats disposed about the periph- -ery of the impellerand partly by the gradual deceleration of the streams discharged fromsaid throats in the curved tapered manifold. Thereby the gas bubbles arepermitted to agglomerate through a relatively long, slow travel. Anunsize.

`less load upon the bearings,

usually small discharge or separator chamber may be employed. Kineticseparation may be largely or wholly avoided with the consequent favoidance in loss of head and consumption of en particularly in theliquid and facilitate the construction of pumps of thel'self-primingtype and reduce the cost` of a pump of a/given capacity..

A feature of the preferred form of the pump of the present invention isan improvement of the balance ofthe impeller which tends to impose andvsubstantially eliminate or reduce noiseancl vibration. 'I'hereby thewear upon the lpump shaft packing is greatly reduced and substantialtightnessis more easily maintained, and with less friction.

A further improvement of the preferred form of pressure attainable froman "impeller of a given n A further object of the inventionis to providea more compact pumping unit.

According to the preferred form herein-,disclosed, a separate bearingfor the impeller shaft need not be provided, as the impeliershaft formsmerely an' extensionof the motor shaft and the bearings of the motorare. when the impelleris thus adequately balanced, amply suficient toguide and 'suDDQrt the impeller and its shaft. The pump unit may thus bemade much shorter .in an axial direction and the cost of the unitmaterially decreased.

Other and additional objects will appear from the following detaileddescription and claims.

In the drawings:

v Figure 1 is Aa. vertical longitudinal section' through a pumpembodying my invention, showlng certain of the parts in elevation;

Figure 2 is a plan viewl of the pump end of the unit shown in Figure 1;i

. `Fig-ure 3 is a vertical cross section taken on the line 3 3 of Figure2;

. Figure 4 is a developed diagrammatic` view lllustrating the iiowduring the priming phase;

Figure 5 is a similar developed view illustratingl the flow duringliquid pumping; Figures 6 and 7 are line diagrams illustrating the flowof the liquid .during primingand during liquid pumping, respectively;

Figure 8 is a sectional view, largely diagrammatic, `illustrating aself-priming pump having two pairs of throats;

Figures 9 and 10 are line diagrams illustrating the ow occurring in thepump of Figure 8 dur-` ing primingand liquid pumping, respectively;

Figure 11 is a side 12 is a plan View of pair of throats placed so as tosecure a balanced operation during liquid pumping;

Figure 13 is a top plan view and Figure 14 a front elevational view of amodified form of pump, largely diagrammatic, illustrating an alternativemethod 'of securing the required unbalance between two sets oi throatsto initiate and maintainthe priming action; n

Figure l is a diagram of a pump employing two pairs of throaillustrating a condition of iiow unbalance when just the iight amount ofelevational view and Figure the present invention is an increase indelivery a pump employing a single and in suitable driving relation.

priming liquid enters both bypasses or auxiliary passageways;

Figure 16 is a similar diagram, illustrating the action` of the pumpwhen one bypass or auxiliary passageway supplies more liquid than isnecessary, with compensation upon the other bypass or auxiliarypassageway; and

Figure 17 is a similar diagram, illustrating the action when thepressure difference is great enough to compel compensation on or`auxiliary throats.

Referring ilrst to Figures 1, 2 and 3, the unit herein shown comprises acommon base I, the pump unit 2 and the motor unit 3.

The -base I may be a continuous castingJ for 15 supporting both the pump2 and the motor 3 or' it may be built up, as herein shown, of a, pair ofchannel bars 4 4 with transverse barsf5 5 con'- necting the channel bars4 4 to provide a sultable attachment forthe pump, similar cross'bars 6 6upon the channel bars 4 4 for providing a suitable mounting foruthemounting legs or lugs 1 1 of the motor.

'I'he pump unit comprises a main annular holbcth bypasses 1o Y and apair of 20 low casting 8 which has an inwardly extending 25 annularprojection or nange 9. 'I'his ring or iiange 9 forms the inner peripheryof the im-v peller chamber, in which the impeller I6A is mounted torotate.

The inner periphery ofthe ring 9 is machined 30 to provide a cylindricalsurface embracing fairly closely the impeller Ill. The ring has taperedshoulders I3 I3 at the sides of the cylindrical bore I2 and it hasradial faces I4 I4 against which are adapted to rest the Y the front andback plates I6 and I1, respectively. 'I'hese plates have osets I8 ofsimilar` contigui-af tion with their outer -sloping surfaces machined tofit the sloping surfaces I3 I3 on the ring 9.

The plates I6 and I1 are machined to provide .40

parallel* annular surfaces adjacent the cylindrical surface I2 toprovide a raceway in which the.

outer ends of the blades`of the impeller I6 are"A confined. A clearanceat I9 between -the back face of the impeller and the adjacent face ofthe 45 back plate I1 is provided. The impeller' I0 is an openimpellerhaving arms such as 26, the outer ends of which are-curved backward withrespect to the direction of rotation, as indicated at 22 center, axiallyprojecting vanes 23 to assist the entering liquid in taking up themotion of the blades or arms 20, so that the liquid, in entering theimpeller chamber, is accelerated rotarlally in Figure 3. These armshave, adjacent the 50 and radially with as little shock, or sharp change55 in direction as it is feasible to secure.

The back plate I1 has a boss or hub 24 which is counterbored to receivethe packing 26 i'orv packing the impeller shaft 26. 'I'he impellerthereupon, the shaft 26 in this case being pro' vided with an axial boreto receive a tie rod 21 for holding the end of the impeller shaft 26 andshaft is here shown as having the impeller cast the end of the motorshaft 28 in axial alignment 'I'he motor shaft 28may be providedwith acentral bore and the tie rod 21 extended completely therethrough. Due tothe balanced load upon the impeller I6,

separate bearings for the impeller shaft are not required, the bearingsof the cient to support run true.

'I'he packing 25 `is motor I being sumthe impeller and to' cause it toheld in place and is com the peripheries 2,110,883 annular recess 32with which the grease cup 33 communicates. opening 32 is closed bypacking received' in the inner recess in the outer end of the follower3l! and in turn compressed by the second follower Il. The follower 3l isurged to the left by a pair of compressiony springs 35, one on each sideof the" shaft, these springs resting against a stirrup formed integralwith the follower 3l at their left hand end and at the right hand endagainst a movable abutment which in this case is a hand wheel 33threaded on the stud 31 abutting against the bearing of the motor 3.

The motor 3 3l having an integral bracket 33Vwhich terminates in asuitable clamping flange l0 and which is clamped against the flange I5of the rear plate Y I1, as will be later described.

The packing sageways 42 formed in the hub 2l, and water circulatingpipes |3443 connect to said passageways through the medium of the plate44,.. which is clamped to the end of the hub 2l.

The top of the bracket 39 is provided with aslot through which extendsthe connection for the grease cup 33 to the pump connection from thegrease cup l5 extending to `the motor bearings I6 passes through thesaid of the bracket member 39 are to the packing gland for tending intorecesses in the back and front plates `l1 and I6, respectively,-and saidflanges are engaged by clamps 52--52 mounted upon the bolts -53, thesebolts being suitably spaced about of the clamping through the ring 9 insuch posiinterfere with the said ring 9, as will ,be de-V tendingaxially tions as not to extending through scribed later. V"I'he clamps52-52 rest in an axial direction against the outer edges of the clampingflanges l0 and 5l, and in a radial direction with respect to the. axisof the pump rest against the adjacent cylindrical shoulders SI--Sl ofthe hollow casting l. d

The intake trap l! is provided with a pipe flange 55 for connecting to`a suction pipe;v An

. opening through this flange extends to the top of the trap l! which,is separated from the bottom by a wall 66, through` an opening in whichextendsthe inlet strainer 51. cover 5l, held in place by the clampingyoke 59, permits access to be had to the interior of the strainer 51.

The vcasting! contains the separating charnber 30 (see Figure 3) andprovides also two circ'umferentially extending passageways 62 and 63,disposed side by side, separated by a central wall Il. -This centralwall il terminates at 65, short of the separating chamber GII.

Referring now to Figure 3, there are shown three pairs of' dischargepassageways distributed about the inner peripheryof the impellerchamber, these discharge passageways comprising the The outer end of theannular throats $6,

is provided with a special end bell gland is cooled by suitable pasthirdmain discharge throat, 6B.

vor manifold 63. It

. cated therein,

the same.

flanges and exf A removable cap or v or' main discharge passageways orB1 and 6B, disposed at 120 with respect to each other, and auxiliary, orposterior passageways or throats $9, 10 -and 1I, respectively.

These throats are all substantially tangential withrespect to themovement of the impeller. The throat 86 is continued as a passageway 66awhich opens into the circumferentially extending duct or manifold sideofthe dividing wall 6l as viewed in Figure 1. 0n the plan view v shown indotted lines, and similarly the continuaanterior tion or passageway 66awhich is shown in dotted lines turns to the right as viewedin Figure land discharges into the manifold or .duct Likewise, the throat 61 iscontinued way 61a, bending the duct or manifold 62.

as passage- The same is true of the v It extends as a passageway overinto the duct or manifold 62. The manifold or duct 62 then, in turn,opens into the separating chamber 60. The chamber 60 has a dischargeopening 12 provided with a surroundin'g bolting flange 13.

The posterior, or auxiliary throats 69, `'Illand 1| `likewise havecontinuations comprising passageways 69a, 10a and lia, opening into ,theduct is to be observed that the that is, occupy full axial length of theimpeller channel,.and since'the wall 6l is disposed substantially in themedian plane of the impeller, the wall 6l is bulged to provide throatsand passageways. suitable for leading liquid out or in, as the case mayof the impeller blades. l

Referring now to Figures 4 and 5, I have indimore or development of thecircumferentially extending ducts or manifolds 62 and 63, and the way inwhich the discharge VOnlyl two pairs of throats, namely, the pair Sli-1I and the pair 61-10 'are herein shown. The ends of' the passagewaysand the 4manner in which they direct flow into the ducts or'manifolds62-63 is indicated in Figure 4, which shows the flow of liquid duringthe priming phase of operation. f v j Figure 5 shows the ow of liquidduringthe pumping phase their connected passageways discharge inparalrignt hand over into communication with I full width of theimpeller,v

be, across the full width" less diagrammatically, a'

throats communicate with when Aboth sets of throats and lel into theducts 62-63 and these in turn discharge in parallel intol the chamber 6Dand out through the flanged outlet opening 12.

A comprehensive understanding of the the fluid during the two stages ofoperation may be obtained from Figures 6 and 7, and later by referenceto Figures 15, 16 and 17 for the compensating action.

, Assume that the suction flange is connected to a'suction pipe and thedischarge flange 13 to an open discharge pipe, the pump being providedwith a suitable priming rcharge, which maybe the amount trapped in theintake trap, pump casing and passageways after a. period of operation ofthe pump and the flowing back of liquid from the open discharge pipeback through the pump, intake trap, and into the suction pipe to breakthe vacuum therein. It will be observed that permits air to pass chamberpassageways s through the discharge ducts and as much liquid as can bedrawn from the intake trap 48 enters the pump casing and is dischargedthrough the various throats of the pump. If suiiicient liquid wereimmediately available to ll the runner, all six of the throats wouldcontinue to operate as discharge throats, discharging the liquid in twoparallel groups of three into the manifolds 6 2 and 63, and they, inturn, discharging in parallel into the separating chamber 60. However,such action cannot continue, since insuiicient liquid is provided forcontinued operation of the pump as a liquid pump. The discharge of apart ofthe priming liquid into the discharge passageways and separatorimmediately causes a deficiency of liquid in'the impeller chamber, withthe'result that the pressure upon the vthroats rapidly dropsA and liquidtends to rethrough the throats-into the Immediately upon the retheimpeller chamber it is enter, by gravity, impeller chamber. entry ofliquid into met by the rapidly ture of air an'd 'liquid -is formed and,by the centrifugal eil'ect oi the impeller, the mixture is driven outthrough the throats. However, since there is insuiiicient enteringliquid to develop a full hydraulic pressure, and since the anteriorthroats are of suiiicient capacity to carry out substantially allrof themixture which is formed. they rob the posterior throats and insufficientprevent the reentry of orderly recirculation is established, asindicated in Figure 6.

The amount of return flow depends upon the size of the-auxiliary orpriming passageways and the difference in pressure or head between theseparator and the inner ends of the passageways where they enter thechannel.

of liquid in the impeller chamber, which, under the action of theimpeller, entrains air and acquires centrifugal force to securedischarge at the main discharge ports. The second body or pool is thatin the separating space of the separator and adjacent parts of theducts. It also is a transient body being constantlyreplenished by liquidwith entrained gas.- 'I'he gas is liberated, and the liquidsubstantially free of gas .pinges 'upon the next succeeding auxiliary orreplenishes the liquid pool or body in the impeller chamber. By thiscontinuous interchange or circulation, the gas in the-impeller chamberand the connected suction pipe is evacuated.

I f the return of liquid through one of the auxilia'ry or priming portsisin excess of that which when mixed with air can be discharged out of vthe nearest discharge port, the excess is carried through a greaterangular distance than `that in which normal pressure is developed, andit iml normal for priming,

ffold ,B2 into, the separator chamber 6|). 4manifold 62 is of the streammoving blades and a mix- As the lsuction 'A is increased there is atendency to increase the priming port, thereby tending to Areduce orstop the return of vliquid port. This provides 'an inherent stability ofaction, maintaining proper distribution of the liquid charge in the twoAfunctionally separate bodies. Evacuation thereupon proceedsy in astable efficient manner'.

When liquid is drawn into the impeller chamber through the suction pipe,the amount of liquid inthe transient working body or pool in theimpeller is-increased above and, asa result, the entraining action isreduced, and the pressure upon all the throats is increased withresultant discharge of liquid at all the original entraining pool orbody is present inthe impeller chamber. If at any time the iniiow ofliquid from the suction pipe fails, the pump reestablishes the primingaction above described.

Liquid is discharged through the duct or mani- The preferably of avolute coniiguration for the dual purpose of reducing the velocity andalso of stratifying the same to assist ,in agglomerating the air intoAlarger bubbles. The stream is turned back in the opposite direction inthe chamber 60, with the result that satisfactoryseparation is securedin unusually small space. The proportioning of the volute dischargepassageway 62 may be such as to effect sufficient reduction of velocityto provide the major air separating action. The most difcult part ofseparation is to agglomerate the minute bubbles into bubbles ofsufficient size to make a marked difference in specific gravity ordensity. For ltwo bubbles to agglomerate when adjacent to each otherthere must be allowed a certain amount of time for the nlm of liquidbetween them to thin out and break. Turbulence ports, both main andauxiliary. The pump strives as it were to reduce the` through saidsecond auxiliary Y that which is l of the mixture tends to separate suchbubbles before the skin or film between them breaks', whichlatter-action is a necessary action before they oin. Agglomeration offine. air bubbles is fostered by concentration of the entrained air in apart of the mixture. For'example, if a uniform mixtureof air bubbles andwater be treated to cause all the vair bubbles to gather in one partvofthe liquid, they tend to agglomerate by the greater tendency to'contact/ each other, and longer period of contact. Concentration of theair bubbles in one part of the mixture may be secured by a number ofdiierent actions. mode employed in the present case is to reduce thevelocity and turbulence of the mixture stream.

This permits, rst, of gravity concentration, and second, of longerengagement or contact between adjacent bubbles, with consequentagglomeration of air bubbles, even if no free surface is present.Another mode also employed, preferably in minor degree, is concentrationby inertia effect as, for example, by causing the liquid to follow acurved path. The denser fluid, i. e., the water with less entrained air,seeks the outer side of the path and the less dense fluid, i. e., thewater with more entrained air, seeks theinner part of the 1path, andeven if no free surface is presented `in the path, agglomeration occurs.'I'he removal of the agglomerated air is then readily eiected byproviding a free liquid surface. This surface need not be quiet, like apool, butmay be moving, as in y* the case of a stream, a whirlpool, orthe like.

One-

operate as a liquid pump, and does so for the major part of itsoperating life, it is highly im- `In the construction shown in Figures 1to 5 the agglomeration occurs by reduction in velocity and reduction inturbulence, and also by the inertia effect, i. e., change in directionof flow. A highly developed inertia effect, or whirlpool, requiresrelatively high velocity of whirl and sufcient diameter and confinementto allow a free whirl to be established. While it is quite effective,and desirable in some cases.A I find it to be undesirable where highefficiencies are to besecured, because of the loss of energy andinterference with delivery when the .pump is operaton a vertical' axis,or it may be secured by providing suillcient space to permit the air inthe liquid to be separated by gravity or in any other preferred manner.While I have shown the liquid as being whirled in the chamber G duringthe priming phase (see Figures 4 and 6) it is not essential that thewhirling action be employed, as gravity separation may be suflicient.Obviously, the chamber 6|) may be made larger and the mixture introducedat high velocity to secure pure centrifugal separation.

The shape of the ducts 62 and B3 is, in general,

thatl of a volute, that is, a constantly increasing passageway extendingcircumferentially of the pump chamber and in the design herein shownthere is a tendency for the liquid to stratify' upon the outer wall ofthe duct or manifold 63. This may be so controlled as to assist inthe-final separating of gas from liquid, or it may perform substantiallythe entire function of separating gas from liquid during priming. j

As soon as liquid enters the intake connection l1 in suiilcient volumeto fill the impeller, the quantity to be discharged increases beyond thecapacity of the throats 66, B1 and 68 to carry the same, .with theresult that pressure is developed in the throats 69, 1li and 1I, andoutward flow in said throats and passageways intothe duct or manifold 63occurs. Thereupon, both the main throats 65, 61 and 68, and theauxiliary throats $9, 10 and 'Il become discharge throats, and

both ducts or manifolds 62 and 63 become discharge passageways,discharging liquid in paral.

lel to the chamber 6U and out through the discharge pipe connection.

I have found that by this construction a great increase in capacity fora given size of impeller is secured, and surprisingly high efficienciesare attainable. At the .same time, the air handling capacity of the pumpis greatly increased over known 'forms of pumps and the device operates,

' quietly and smoothly to a degree not heretofore attained in anyself-priming pump with which I am familiar.

While I have described above the preferred em bodiment of the inventionit is to be understood that certain advantages of my invention may besecured without embodying all of the features thereof. f

Since a pump of this character must-essentially portant that theefficiency of the 'pump and' its balance, when running as a liquid pump,be made as good as possible. v

In Figures 15, 16 and 17 I have indicated the novel mode of compensationinvolved in the operation of the pump of the present invention'. Whilethese diagramsishow only two pairs of throats it is to be understoodthat the mode of operation and the same principles are involved in threepairs of throats or more. During the priming stage, the impellerperforms two chief functions, the first of whichis to form a mixture ofgas and liquid, and the second of which is to discharge the same fromthe pump casing through the discharge throat or throats. The two actionsare in large degree antagonistic, in that the development of centrifugalforce tends to disentrain the gas from the liquid, that is to say,therel is a tendency for the air to be' squeezed radially inwardly asthe same is' carried about,

due to the development of centrifugal force. It

is therefore apparent that the denser fluid is radially outermost andthe lighter fluid, that is, the mixture of air and liquid containing thegreatest amount of air, lies radially inward. Itis desirable to carrythe liquid no further angular- 1y than is necessary to develop thedesirable pressure. My 'present form of pump greatly reduces the angularcarry of the mixture, as compared with previous forms of self-primingpumps, and

thereby less disentrainment ofA the air occurs. Also, in the liquidpumping phase, it is undesirable to carry the liquid any furtherthan isnecessary to develop discharge pressure, and by reducing the angularcarry, as I have done in the pump of the present invention, I havereduced v the eddy current losses within the casing and I find, as amatter 'of fact, that the discharge pressure attainable with the samediameter of impeller is actually greater with the short angular carry.

Since -the mixture tends to stratify, due to the centrifugal forcedeveloped by rotary motion, any greater. depth of liquid in the pumpchannel than can be discharged through the discharge throat results in adischarge ofthe liquid containing ythe least air, whereas it isdesirable to carry out of the casing the liquid containing the most air.

Hence, it will be apparent that if the return flow of liquid is greaterthan that required to fill the discharge throat or throats, the excessof liquid is not only undesirable, but actually hinders the rapidevacuation of the casing andsuction pipe.

V'Ihe rate of return ow of liquid from the separa- `tor to the pumpcasing through the by-pass or auxiliary passageway lis controlled by thedifference in pressure or head prevailing on the bypass or auxiliarypassageway. As the vacuum in the pump casing increases, `greaterdifference between the pressurein'the separator and the pressure Vin thepump casing arises, with consequent increase in the rate of returnYflow. This same difference in pressure tends to oppose the outflow ofliquid' at the discharge or main throats, but such difference inpressure is relatively minor compared with the discharge pressuredeveloped by operationV of the rotor, and hence no appreciabledifference' in rate lof outflow occurs. But both of these tendencieswork in the direction of returning fthe circulating water from theseparator to the pump casing more rapidly. This may v result, if notcounteracted, in an excessive amount of liquid being present in the pumpcasing. It is here that the automatic compensation which is illustratedin Figures 15,' 16 and 17 assists in controlling the return of liquid ina manner which is highly benecial to secure more rapid evacuation andgreater eiciency of evacuation than has heretoforebeenpossible in pumpsof this class. In the diagrams of Figures 15, 16 and 17 the primarythroats or discharge throats are indicated at A 'and A'. The auxiliarythroats or by-pass throats are indicated at B and B'. The arrowsindicatethe direction of flow, and this flow within the casing ismaintained by rotation of the impeller.

Figure. 15 illustrates a condition of ow balance when just the rightamount of water enters both by-passes. Hence the incoming stream from Bmeets the impeller, which mixes it with air, and the mixture is carriedaround and all of it is discharged through the throat A' into the,separator, it being understood that all of the throats are connected tothe separator. Similarlmliquid from the separator entering the throat B"meets the impeller, is mixed with air, and all discharges through thethroat A. This is the ideal condition, and vassuming that the pumpstarts with no difference in pressure between the separator and' thepump casing, the design may be such as to secure initially suchcondition of operation. As soon, however, as a greater pressuredifference occurs by carrying out a part of the air from the pumpcasing, the condition shown in Figure 16 begins to prevail. IIn thatcase, one of the auxiliary or by-pass throats, for example B, assumesthe controlling action. More liquid ows through the throat B thanheretofore because of thegreater difference in pressure on theends ofthe throat, and a larger quantity of liquid is carried on the left handside of the diagram, as indicated. Since the throat A' cannot dischargeall of the liquid carried by the impeller, a part of the mixture asindicated in Figure 16 is carried past th'e main throat A', and createsa pressure condition upon the throat B'," tending to retard the flow ofliquid from the separator through the bypass B' intothe pump casing. Thesame difference in pressure which operates on the throat B operates onB', but because of the opposition of the excess liquid carried by thethroat A', throat B' is not able to supply the same amount of liquidthat is supplied by the throat B. The excess which has been introducedat B thereby prevents excessoccurring at the throat B', and conditionsmay be so selected as to permit the mixture, consisting of the liquidcarried by the throat A and introduced by the throat B and mixed withair, to be fully discharged at the throat A. Thus it will be seen thatalthough the left hand part of the pump is working at some disadvantagefor the evacuation of air, the right hand half in Figure 16 is stillworking at a high eiilciency for the evacuation of air, because not onlythe heavier iluid, but also the lighter :duid containing more air, isbeing carried out the main discharge throat A If the diierence inpressure between the separator and the pump casing is further increased,then conditions such as shown in Figure 17 may prevail.

In this case there is illustrated the action when the vacuum issuilcient to make both by-passes tryto feed too' much water. B stillsupplies more than B'. Both discharge throats are properly filled, andthe excess from B tends to compensate or balance the action of B', thetendency of which is to supply an increased amount, 1314i' the tendencyis not completely overcome, and some oi.' the excess liquid by-passingA' together with the liquid entering at B' is carried past the maindischarge throat A, and begins to compensate on the flrst main throat B.The mutual control of the by-passes upon each other may.

be interchangeable, that is, either one may initially sieze control orpreponderance.

The result of the above described mode of op-l eration is thatevacuation ofA air is more rapid. There is less disentrainment oi airdue to the shorter travel, and a higher degree of vacuum can be reachedthan has heretofore beenpossible in pumps of this type. It is generallycustom-` ary to make each of the by-passes with an area of about of themain throats. It is desirable to make the capacity o f the by-pass`throats'i'airly large, since they become discharge passageways uponfilling of the suction pipe and the pump with liquid. By the scheme ofautomatic and progressive compensation, the throats may be made so largethat they would supply far more priming Water than is required ifcompenf sation were not effected.

Obviously, while I have illustrated two pairs o1.'

throats, this invention is not conncd to twol pairs, nor is the actionany different if more than two pairs of throats are utilized. Either oneof the by-pass or priming vthroats may assume kpreponderance to dominatethe return flow. of liq'- uid, lt being a matter of indifference in theoperation ofthe pump. Obviously, by suitable def sign, a particularthroat may be given the dominating action. In experiments which I haveconducted, the self-compensation, that is, the

carrying of liquid from the throat B clear back to itself, asillustrated in Figure 17, does not occur until vacua around twenty-tiveinches or bet.`

ter are reached.

By the provision of a common separator connected to all of the dischargethroats and the return throats in parallel, the action of the pumpduring priming, particularly as to the exterior path of the primingliquid, is stabilized, and the eiciency of the pump improved. Thiscommon separator equalizes the Work of the various pairs of throatsduring priming. The separation of gas from liquid is also improved,particularly bythe employment o f the two manifolds between thedischarge throats and the separator.

The discharges of all the anterior throats, such as 6E, 61 and E8, enterthe manifold and are mixed and equalized both in the manifold and in theseparator 60, and the agglomeration of gas bubbles is promoted. Theposterior or auxiliary` adjacent anterior throat, the tendency to cause:fluctuations inI pressure or surging is greatly reduced or prevented. f

The external part of the priming circuit is stabilized and equalizedthrough the usev of the common separating chamber. 'Stability andleficiency of priming is promoted in the internal part of the primingcircuit by a hydraulic com pensation as between liquid entering one-inlet l pump in Figure 1,

the auxiliary, -or

- in illustration. When the pump is axiomas 4a capacity about 80% throatand liquid entering another inlet throat as heretofore described. Thepump as a whole has a pronounced inherent stability. 'Ihis isparticularly important because of the relatively small amount of primingwater which the pump employs for the amount of gas which is handled.

In the pump herein shown, particularly the the discharge' manifold 52blends together the discharge streams of mixture and provides apreliminary separation of the gas fromthe liquid before the streamenters the separator 58. Here the gas rises out through the outlet 12and the liquid passes through the priming manifold 53 towards thepriming throats. In this manifold during this action, the liquid isfurther equalized, particularly as to gas content, so that substantiallya uniform quality is supplied ,lat each of the priming'throats. Thusthese manifolds, by the perfomance of new functions, secure new resultsorY results which were performed less advantageously in the separator ofprevious self-priming pumps.

` The efliciencies attainable are comparable with those of the bestclosed impellertype pumps, with allI the simplicity of construction andclearances of the open type impeller.

It is not essential in the construction of the p pump that the circulararrangement of manifold here shown be employed. The throats maycommunicate directly with the separator. chamber, or two chambers mightbe employed.

While I have shown three pairs of throats in the pump of Figures 1 to 'lit is to be understood that any number of pairs which is found suitablemaybe employed, but I also wish to point out that it is not essentialthat the throats be arranged in closely grouped pairs. For example, inthe structure illustrated in Figures 11 and 12, there are providedonlytwo throats, and 18, placed diametrically opposite each other withrespect to the axis of the impeller. 'I5 and 16 communicate with theraceway f or the impeller blades within the pump casing and communicatethrough separately formed ducts, or passageways 18 and 19, respectively,with a vor.- tex separating chamber 88. Obviously, anyother form ofseparating chamber may The two conduits `|8 and 18 open substantiallytangentially into the cylindrical separator chamber 81|. An inlet trapis` provided for the inlet 28, this being omitted for the sake ofsimplicity started 4up it is provided with a suitable priming charge,and assuming that the impeller chamber stands filled with water, thedifference in the hydrostatic head upon the throats 15 and 18 issuflicient to start an unbalanced action. At the same time, the

friction of the passageways 18 and 18 also assists in establishing aproper direction of flow. Since the hydrostatic head on the throat 15 isless than the hydrostatic head on the throat 16, assuming substantiallyequal pressures to be caused by the motion of the impeller Il), there isa tendency to drive the liquid out of the throat 15 'more easily thanout of the throat 1G, and hence circulation in the direction causing thethroat 15 to be the main discharge throat and the throat 16 to bepriming throat, is usually instituted. If the throats are of the samecapacity it is immaterial which one assumes the discharge function andwhich one the priming function during priming. I have found it generallydesirable where the' throats arey arranged in pairs, to

make the posterior throat of the pair, which throat becomes the by-passor priming throat, of

, arator sure to occur at said throats,

These two .throats be employedi 7 of that of the anterior or dischargethroat. served inthe present pump when one throat is Vdesigned to assumethe priming function.

It will be observed that where only a single pair of throats such as 15and 1B are disposed diametrically with respect to each other', duringpriming one half of the impeller periphery is all that is doing activework. This unbalances the thrust radially on the impeller shaft duringpriming', but as soon as liquid pumping -begins the effect is balanced,or substantially so, since liquid enters axially through the inletopening and moves radially in all directions to fill the impeller llland to be thrown out on two sides of the same. whereby the radial forcesare substantially balanced. I

In Figure 8 I have shown how two pairs of throats may be employed in apump of this char- 1 acter to secure a balanced effect during bothpriming and liquid pumping. j

In this case the main or anterior throats 15 and 1B are connected to amanifold or duct 82 which, in turn, leads tangentlally into thesepchamber 88 for providing centrifugal separation. The posteriorthroats 83 and 8l are connected to the separator 80 by a duct ormanifold 85. The form of separator and its mode of operation isoptional.

'I'he operation of apparent Vfrom the diagrams of Figures 9 and y10 andfrom the foregoingdes'cription. The'anterior throats 15 and 15 rob theposterior throats This proportion may be obthis form of device willbeyand 84 of liquid, causing regions of reduced preswith the result thatwhile liquid, or liquid mixed with gas, is discharged out of theanterior throats into the separating chamber, liquid from which gas hasbeen separated in the chamber 80 is returned through the throats 83 and8l into the impeller I8. each half of the impeller l0 is used equallyduring both priming and liquid pumping, the balanced effect which it isdesired to secure is thereby attained during both phases of operatori.

In the diagrams of Figures -7 and 10 the axial iniiow'of liquid and itsmovement by theimpeller is indicated by the lines 815-85.

In Figures 13 and 14 I have illustrated a modifled form of construction.In this lcase the primary throats, or throats which are invariablydischarge throats, are indicated at 81,- 88 and 88. They are connectedby passageways 81a, 88a and 89a with the duct or manifold 8D whichdischarges into the separator 88. Equally spaced angularly with respectto the primary discharge throats are the auxiliary discharge throats 82,83 and 94.

All of these throats, instead of discharging tangentially with respectto the inner cylindrical wall 95 of the casing 85, discharge laterallytherefrom. The throats 92, 93'and 94 are connected by short passageways82a, 93a and 94a with the duct Since` or manifold 91 which also leads tothe centrifugal discharge the mixture of air and liquid -during thepriming phase out of the throats 81, 88 and 88 and to securereentryithrough the throats 82, 93

widening the outer, or

Obviously, instead of having the throats all equally spaced angularlyabout the periphery oi the casing, these throats may be grouped in pairsif desired.

Also, while I have shown lboth groups of throats as opening axiallyinstead of tangentially, the group of primary throats 81, 88 and 89 maybe disposed tangentially and the auxiliary throats arranged to openaxially. Also, if desired, tangential throats for the primar'y'dischargemay be provided and axially disposed throats registering with each otherfrom opposite sides of the casing may be provided. In this case threeducts, or manifolds would be employed, the primary duct openingtangentially into the separator 80 and the return duct, preferablywith acommon opening from a lower point in the separator 8D, if desired.

From the foregoing it will be seen that various methods of producing thedesired unbalance in pressure inthe two sets of throats may be employed.The preferable embodiments are those in which `the reaction of thevarious throats is balanced substantially radially and axially upontheimpeller, soy that it may run substantially without the necessity forguiding bearings. In the construction shown in Figures l to 3,inclusive, the impeller shaft is short and forms merely a rigidextension of the motor shaft Without requiring any bearings in additionto the /motor shaft bearings. Where the impeller tends to run true bybalancing the stresses thereupon it is much simpler to maintain thepacking tight and far less wear upon the bearings occurs.V

-While I have shownxa'form of impeller-which ishighly advantageous, itis to be understood 'that the invention is not limited to this specioform. The impeller is substantially self-balancing in an axial directionduringboth the priming phase and during the liquid pumping phase. Theforwardly extending vanes 23 of the` impeller Ill assist in directingthe liquid and giving it the proper motion to enter the actual workingspace or channel in which the blades or arms of the runner move, so asto secure a gradual acceleration,A both axially and radially, as well ascircumferentially.

I do not intend to be limited to the details shown and described, exceptas they are recited in the appended claims. It will be apparent to thoseskilled infthe art that various modifications and refinements will atonce occur'to'those skilled in the art, all of which are contemplatedvas coming within the spirit and scope of my invention.

I claim:

1. In -a self-priming pump,'the combination ofa casing having a centralAinlet and containing a channel for an impeller, an impeller lying in avertical plane and being mounted on a hori-` zontal axis to run in saidchannel, vthere being an even number of substantially tangentialdischarge outlets from said channel, the maximum angular distancebetween adjacent outlets which are connected to different ing itslongitudinal axis disposed substantially vertically, a first passagewayserving always as a discharge passageway connecting half of saiddischarge outlets to said separator at one side of the axis thereof, anda second passageway serving on the priming phase'as a priming passagewayand on the liquid pumping phase as a discharge passageway connecting theother half oi' said outlets to the separator at the other sidepassageways being notl ,a separator havof the axis thereof, saidpassageways opening -into said separator substantially horizontally andatl -substantially the same level, said separator having an outletopening at the top of the same.

2. In a pump of the class described, the combination of a casingproviding an impeller chamber and an axial inlet, said chamber having apluralityof pairs "of throats disposed about its periphery, a separator,said pairs of throats beingfspaced angularly about said periphery bygreater angular distances than are the throats of each pair, saidangular spacing between adjacent pairs of throats being notsubstantially Agreater than that within `which the mixture of gas andliquid receives its full discharge velocity from the motion of theimpeller, each pair of .throats comprising a main discharge throatserving always for discharge of liquid, and an auxiliary or primingthroat, serving during priming for the return of liquid from theseparator to the impeller chamber, a duct connecting all of the main'throats to the separator, and a duct connecting all of the auxiliarythroats to the separator, said ductsy and separator serving to stabilizethe action of the pump during priming.

3. In a pump of the class described, the combination of the casingproviding an impeller chamber and an axial inlet, said chamber having aplurality oi pairs oiL throats disposed about its periphery, each paircomprising a main throat and an auxiliary throat,as'eparatorchamberhav-- lng a cylindrical wall, a manifold ductconnecting the main throats and leading the discharge there` of into theseparator chamber substantially tangentially of said cylindrical Wall,said duct producing agglomeration of air bubbles of the mixture of airand liquid discharged thereinto, a second manifold,A duct connecting theauxiliary throats with the separator chamber, said ducts extendingperipherally of said impeller chamber, said ducts and separator servingto stabilize the action of the pump during priming.

4. ,In a pump of the`class described, the combination of a casingproviding an impeller'chamber and an axial inlet, said chamber having aplurality of pairs of throats disposed about its periphery, each paircomprising a main throat 'and' an auxiliary throat, a separator disposedat the upper end of the pump icasing. said casing vcomprisingv a\hol1owannular portion encircling 'the impeller chamber, a dividing wallextend'- ing around the, major part of thenpehiphery and dividing saidhollow annular portion into two passageways which terminate in saidseparator,

-said main throats being connected to one pasvsageway and the auxiliarythroats being con-w nected to said other passageway.

5. In apump of the class described, a hollow annular casing having twoperipherally extending passageways constituting manifolds and hav' ingan enlargement with which said passageways lconnect, constituting aseparator chamber with an outlet for gas during priming and for liquidduring liquid pumping, a plurality of pairs of throats,v said lpairs ofthroats being equally spaced about the inner periphery of said casing,each pair comprising a main discharge throat and an auxiliarythroa't,the main throats communicating with one passageway and the auxiliarythroats communicating with said lother passageway, a pair -of sideplates cooperating with said annular casing to define an impellerchamber, and an impeller in said impeller chamber, said impeller havinga shaft mounted in one ofsaid plates, the other' plate having an inlopening substantially centrally thereof.

6. VIn a pump of the class described, an annular casing having acentrally disposed radially inwardly extending annular ring and a hollowcasing extending about the ring, said casing having an enlargementforming' a separator chamber and having a dividing wall extendingthroughout the major part of the periphery and terminating i short ofthe separator chamber, substantially tangential main dischargepassageways extending through said ring and leading to one side of saiddividing wall, substantially tangential auxiliary discharge passagewaysextending through said ring and leading to the other side oi' saiddividing wall, inwardly dished side plates having margins restingagainst the sides of said rln'g, said ring .and side plates defining animpeller chamber, an

impeller mounted for rotation in said impeller chamber, and boltsextending through said ring outside the margins of said side platesforclamping said side plates against the ring.

'1.4 In a pump of the class described, an annular Y,

casing having a centrally disposed inwardly extending annular `ring anda hollow casing extending about the ring, saidl casing having anenlargement forming a separator chamber and having a dividing wallextending throughout the major part of the periphery and terminatingshort of the separator chamber, substantially tangential main dischargepassageways extending through said ring and leading to one side of saidd ividing wall, substantially tangential auxiliary discharge I peller,an inlet trap having a flange resting against the flange of said inletplate, a motor bracket member having a flange resting against the flangeof the other side plate, and bolts extending through said-'ring radiallyoutside of said flanges and clamping said flanges against said ring.

8. In a self-priming pump, a pump casing comy,

prising an impeller chamber, an impeller mounted for rotation therein,said chamber having an inlet i'or liquid leading into that part of theimpeller lying radially inward of the periphery thereof, a separatorchamber-having an outlet for the iluid discharged by the pump, twomanifolds, and a plurality of pairs of adjacent discharge passageways,said pairs being equally spaced about the peripheryof the impellerchamber and like ones of said pairs being connected by said twomanifolds respectively to said separator, said manifolds and separatorserving to stabilize the action of the pump during priming by poolingthe incoming and outgoing streams.

9. In a self-priming pump, a pump casing providing an impeller chamber,an impeller mounted torun insaid impeller chamber, a. plurality ofsubstantially tangential discharge throats spaced substantially equallyaboutrtheinner periphery of the impeller chamber to provide a multiplethroat discharge, the angular spacing between throats being notsubstantially greater than that in which the liquid receives thenecessary discharge velocity i'rom the motion of the impeller, aseparator towhich said discharge throats are. connected, and apassageway between the sepa-l rator and a part of the impeller chamberwherein pressure is developed by operation of the impeller when it issupplied with water ior returning liquid from the separator to theimpeller chamber during the priming phase whereby return of liquidthrough said passageway during the liquid pumping phase. is prevented,said separator having an outlet through which the pumped uid is dis'-charged, said separator acting to equalize the effect o! saiddischargethroats upon said return passageway during priming. s

10. In a seli'epriming pump, a pump casing providing an impellerchamber, an impeller mounted for rotation in said-v chamber,` aseparator chamber having an outlet for fluid discharged by the pump,there being a plurality of discharge throats spaced substantiallyequally about the periphery of the impeller chamber and all leading tothe separator and servingy at allv times to discharge liquid from theimpeller chamber, the angular spacing between `throats being notsubstantially greater than that'in which the liquid receives thenecessary discharge pressure from. the motion of the impeller, and meansfor conducting liquid from the separator to the interior of the impellerchamber during the priming operation, said means comprising an auxiliarythroat which is subjected to lower hydraulic pressure during the primingoperation than are the discharge throats, saidauxiliary throat beingsubjected to sufiicient hydraulic pressure during liquid pumping thatrecirculation is substantially prevented, said separator serving toequalize the gas content of the liquid returned through said auxiliarythroat.

`11. In a self-priming pump,Y an impeller chamber, an open impellermounted for rotation therel in, a separator, said chamber havingmultiple discharge throats spaced about the periphery thereof to providea'balanced discharge from said impeller, and a plurality of ductsconnecting said discharge throats to said separator, sad pump beingorganized to compel outflow invariably from the impeller chamber throughall of the throats and through both of the ducts when the pump `ispumping liquid, and to compel return iiow from the separator through'one of said ducts and at leastv one of said discharge throats when thepump is operating on the priming phase", said ducts being .disposedlaterally of each other and on oppositey sides ofthe median plane of theimpeller chamber, and having walls formed integral with the Walls of theimpeller chamber.

12. In a self-priming pump, a casing comprising an impeller chamberhaving an inlet opening and having a pluralityof pairs of substantiallytangential throats, an impeller mounted to rotate in\ said chamber, aseparator chamber disposed substantially at the top of the impellerchamber,

` liquid is discharged during liquid pumping serving to ualize thereturn ilow of priming liquid to the throats which are connected to saidother manifold, both as to Y amount and as to Vgas content, and servingto-stabiiize the action ofthe 13. In a self-primingpump, a casingcompris- 7ing an impeller-,chamber vhaving an inlet opening and having aplurality of pairs of substantially tangential throats.- an impellermounted' to rotate in said chamber, .a separator chamber, a pair ofvolute shaped manifolds leading into vsaid separator chamber, thethroats of each pair anterior in respect to the Adirection of rotationof the impeller'being connected to one manifold and the throats ofeachfpair posterior in respect to the direction of rotation of theimpeller being connected to the other manifold, said manifolds lying inplanes substantially parallel with the plane of the impeller, lsaidseparator cham- ,ber being approximately' circular and having itscircular axis substantially parallel to the plane of the-impeller.

14. In a self-.priming centrifugal pump, a

f pump casing comprising a central inlet, an internal channel, a runneroperating ln said channel, there being a plurality of pairs of outletsfrom the channel. a separator chamber into which all of said outletsopen, each pair oi outlets comprising amain outlet and an auxiliary or.priming outlet, said main outlet of each pair being with respect to thedirection of rotation of the impeller anterior to theauxiliary orpriming outlet whereby during priming of the pump the auxiliary orpriming outlet of one pair supplies from the separator chamber liquidwhich is introduced into the peripheral part of the impeller to be mixedwith gas in the casing, some of said introduced liquid beingdischarged-at the main outlet of another pair and some beingcarriedbeyond said main outlet of the other pair,

and the liquid which is carried beyond said main outlet of said otherpair retards the inow of liquid from the separatorA through theauxiliary or priming throat of said other pair into the pump casingwhereby to increaseA the efiiciency and stability of the primingaction.-

15. In a pump, the combination of an annu- -lar frame casting havingv asubstantially cylindrical interior peripheral wall forming the bottom.wall of a channel, there being openings at a plurality ofv substantiallyequidistant pointsv in said cylindrical wall forming throats, theannular casting having a peripheral manifold passageway formed thereinextending partially around the outer periphery of 'the pump and therebeing tangential passageways for conducting fluid discharged throughsaid openings into the manifold passageway, said manifold passage- .wayconducting -the liquid from said throats in the same peripheraldirection throughout, a pair of side plates clamped against saidannular- -frame casting, said plates having planar surfaces cooperatingwith said circular-wall to deline a channel, and a runner having bladestraveling in said channel.

16. In a pump, the combination of an annular frame casting` having asubstantially cylindrical interior peripheral wall forming-the bottomwall of av channel, there being openings at a plurality of substantiallyequidstant points in said cylindricalwall forming throats, the annularcasting having 'a peripheral manifold passageway Kformed thereinextending partially around the outer periphery of the pump and therebeing tangential passageways for conducting uid discharged through saidopenings into the manifold passageway, said manifold passagewayconducting the liquid from said throats in thesame peripheral directionthroughout, a pair of side plates `clamped against said annular framecasting, said .plates having planar surfaces cooperating with saidcircular'wall to denne .a channel, a runner having blades traveling insaid channel, and bolts disposed parallel-to the-longitudinalaxis of theannular casting, saidbolts extending through the annular'castingradially within said mani.- fold passageway and being spaced angularlybetween the tangential passageways, said bolts clamping the side platesagainst the annular casting'.

17. A self-priming pump having a casing pro- 'vided with an inlet, anopen runner, a single separator and a plurality of pairs of passagewaysproviding communication between the casing and the separator, each pairof passageways comprising a discharge passageway and a return passagewayduring priming, said separator serving to equalize the. work of saidthroats and to stabilize the operation of the pump during ,priming andhaving a common outlet for the fluid being pumped.

18. A self-priming pump comprising a casing having a central inlet forliquid, an open runner therein, a single separator, a pluralityof pairsof tangential throats all leading .to the separator and all serving asdischarge passages in parallel when the pump is 'pumping liquid, theanterior throat, in the direction of rotation of the runner, of eachpair serving as a discharge passagewayfor discharging a mixture of gasand liquid from the casing to the separator, and the posterior throat,in the direction of rotation of the runner, of each pair serving toreceive liquid freed of gas from'the separator into the casing whileliquid is'being circulated during the priming operation, said separatorserving to equalize the work of said throats and to stabilize theoperation of the pump during priming and having a discharge outlet forthe uid being pumped.

19, A self-priming pump comprising a casing having a central inlet forliquid, an open run'- .ner therein, a single separator disposedsubstantially at the top of the casing, a plurality of pairs oftangential throats disposed at substantially equal distances about theinner periphery of the casing and all leading to the separator and lallserving as discharge passages in parallel when thepump is pumpingliquid, the anterior throat,

in the direction of rotation`of the runner, of each pair serving as adischarge passageway for discharging a mixture of gas and liquid fromthe casing to the separator, and the posterior throat,

in the direction of rotation of the runner, of

each pair serving to receive liquid freed of gas from` the separatorinto the casing while liquid is being circulated during the primingoperation,

said separator comprising a chamber with a wall curved in a horizontalplane to cause horizontal circular travel of the circulating liquidduring priming, said separator serving to equahze the work of saidthroats and to stabilize the operation of the pump during priming andhaving a discharge outlet for the fluid being pumped.

- 20. A self-priming pump comprising a casing,

an open runner therein, a single separator, a plu-` rality of pairs oftangential throatsalleading to the separator and all serving asdischarge passages in parallel when the pump is pumping liquid, theanterlor'throat, in the direction .of rotation of the runner, of eachpair serving as a .discharge passageway for discharging a mixture of gasand liquid from the casing to the separator, and the posterior throat,in mennen-.ion of rotation of the runner, of each pair serving toreceive liquid freed of gas from the separator into the casing whileliquid is being circulated during the priming operation, said separatorth thev W Sets channel vanchas comprising a substantially cylindricalchamber axis substantially vertical an'd a pair f substantially parallelvolute manifolds for the of discharge throats, said manifolds openingsubstantially tangentially into said separator at. opposite sidesthereof. 21. A self-priming centrifugal having a central inlet ofuniform depth, an open runner having pump, a casing and comprising acircular substantially uniform clearance with the periphery of thechannel, a-- plurality of pairs o'f adiacent throats tangential totheperiphery of the channel, said pairs about the periphery of thechannel.'

uniformly and a. common being spaced substantially separator connectedto all of said throats, anterior ones ,of each pair being connected byby a seco a common manifold to said separator -and posterior ones ofeach pair being connected nd common manifold, said manifolds comprisingvolutes having their outlet ends extending substantially horizontallyinto a common separator chamber and providing additional space withinwhich gas separation may take place, said separator having an outlet forthe fluid being pumped,

with sai`d and serving in combination manifolds during priming toequalize the work upon the throats.

22. In a self-priming pump,

an impeller, a

casing therefor provided with a central inlet and having a plurality ofsubstantially equally spaced tangential 'discharge rator for returningripheral part of the through outlet for throats, a common sepasaiddischarge throats, and means for liquid from the separator to the peisdriven out of the casing throats in parallel during said separatorhaving an fluid being pumped, said separator the fluids dischargedthroats and equalizing the the gas content of said liquid returned tothe impeller during priming.

23. In a self-priming pump, the combination of a runner casing andrunner, said casing having a single central inlet and a peripheralthroats which all separator plurality of pairs of and a common separatorto throats are connected, said an outlet for the fluid being of thehaving pumped, the throats of each pair being so close to each otherthat the runner does not have suillient pressure betweenV them,

angular travel to build up discharge the by only sufficient angulardistance to allow discharge pressure to be built up between them,whereby during the priming operation *the mixture of gas and liquid isnot subjected to unnecessary of liquid centrifugal separation, thedischarge throats during pumping of the axis of the separator to provideparallel discharge flow through the outlet. the fluidstreams dischargedduringl priming from corresponding throats of each pair being allblended in said common separator and the other throats 4 of -each pairbeing supplied with liquid from said common separator, whereby to uponsaid pairs equalize the work of. throats and to stabilize the action ofthe pump during priming.

combination of claim 23,' wherein the pairs yoi! throats aresubstantially equally spaced aboutthe nectcd periphery of the casing andare conby two manifolds tothe separator, one

connecting those throats of each pair anterior in the direction ofmotion of the throats `of each pair impeller Ifor circulation theimpeller and formation of a gas and liquid mixture which through thedischarge priming -of the pump,

pairs being separated l 1 l the runner and the other manifold connectingwhich are posterior in the direction of motion of the runner, thethroats of the first half. discharging in parallel through the firstmanifold to provide a single stream entering the separator.

25. In a self-priming pump, the combination yof a casing comprising aperipheral portion for cooperation with animpeller and having a centralinlet, an impeller having vanes for driving liquid from the centralinlet intothe peripheral portion during liquid pumping, said casinghaving a series of ports disposed about and opening out of saidperipheral portion, a first manifold connecting alternate ones of saidports, a second manifold connecting the other ones of said ports, and adischarge and separating chamber in which gas is liberated from theliquid entering the same and through which one manifold discharges intothe other in series during the priming operation of the pump, saidchamber having an outlet through which gas alonevis discharged duringpriming and through which both manifolds discharge liquid in parallelduring liquid pumping, said ports connectedY to the first manifold beingspaced apart by an angular distance not substantially greater than thatwithin which the fluid being moved acquires full discharge pressure bynormal motion of the impeller.

26. The combination of claim 25 wherein the impeller is an open impellerhaving blades curved backwardly with respect to the direction ofrotation, and wherein the peripheral portion of the casing provides achannel which is substantially 1cylindrical at its periphery, andwherein the separator chamber having a cylindrical inner wall with avertical axis and an outlet at the top, means defining two taperingvolute manifolds extending circumferentially of said ringlike member andhaving their larger ends opening substantially horizontally into thesides of the separator, alternate ones of said passageways leading intoone manifold and the other passageways leading into the other manifold.1

I28. In a self-priming centrifugal pump, the combination of a casingproviding a pumping chamber having a peripheral portion for cooperationwith an impeller and providing a central inlet for liquid to theimpeller, an impeller having vanes for driving the liquid from thecentral inlet to the channel during liquid pumping, a separating anddischarge chamber having an outlet, said peripheral portionhaving aseries of throats all of which discharge liquid in parallel into thesecond named chamber and through the outlet when liquid is supplied tothe inlet, and when liquid supply at thek inlet fails, discharge ofliquid in -parallel ceases and liquid from said second, chamber reentersthe pumping chamber through a plurality -of said throats to be mixedwith air by rotation of-the impeller and gagain discharged into saidsecond chamber, said second at an adjacent point of reentry tending tolimit reentry of liquid at said second point.

29. In a self-priming pump, a pump casing having a single continuouschannel open toward the center of the casing and having an inlet openingcommunicating with the central part of the casing, a single open typeimpellerA running in said channel, a, plurality of priming andldischarge openings disposed at angularly spaced points about saidchannel, the angular distance between a priming opening and its nearestcooperating discharge opening being not substantially greater than thatwithin which the impeller forms and builds up discharge pressure of amixture of air and liquid during priming, a separator and discharge.chamber having an outlet through which gas is" discharged duringpriming andl through which liquid is discharged during 'liquid pumping,a passageway of substantially greater cross section than that of the sumoi' the discharge openings for conducting all the mixture discharged bysaid discharge openings to said separator and permitting agglomerationof gas bubbles as the mixture is being conducted,

and a passageway -leading from the separator to said priming openingsfor the return of priming liquid substantially freel of entralned gas,said separator and said passageways servingto equalize the circulationof liquid in both amount and gas content duringvpriming, all of saidopenings serving as parallel discharge openings when liquid is suppliedto the inlet of the pump.

30. A pump of the class described, comprising y an impeller adapted toreceive liquid axially and to discharge the same substantiallytangentially, a casing having a peripheral portion embracing theperipheral portion of the impeller and having a central inlet for fluidtobe pumped, said casing having pairs of throats spacedabout-saidperipheral portion by angular distances substantially greatenough only to permit the impeller to build up the desired liquiddischarge'pressure between the posterior throat of one pair and theanterior throat of another pair, whereby the mixture of gas and liquidformed during priming is subjected to minimum centrifugal separation, achamber having inlet means through which the liquid from all theanterior throats enters in a posterior throats serving as dischargethroatsv common stream in the same direction during either priming onliquid pumping, whereby during priming the gas contents of said commonstream is equalized, said chamber having a discharge outlet throughwhich gas is discharged during priming and through which liquid is dis--charged during liquid pumping, and conduit means-through which liquidfreed from gas flows from the chamber `to said posterior throats andinto the peripheral part of the impeller during priming,- excessivere-entry at one priming throat` being caused to hinder re-entry ofpriming liquid at the next adjacent primingthroat, whereby `theeflciency of entrainment of gas is enhanced, said .during liquidpumping.

31. In a self-priming pump, a pumping chamber 'with a, central inlethaving an even number peripheral-ly disposed throats, an impeller in thechamber serving when liquidis supplied at the inlet to discharge liquidat all of said throats in parallel, a manifold of relatively great crosssec`- tion at its central part and having an outlet at said central partfor the fluid being pumped, said manifold lbeing progressively reducedin crosssection fromsaid cent part to yboth ends, one half of saidmanifold being connected to alter through the other half of vthe throughthe other half of said throats into thenate ones'of said throats and theother half of said manifold being connected to the others of saidthroats, said two halves of the manifold being curved peripherally aboutthe pumping chamber, and-when liquid at said inlet fails said impellerforming a mixture of air and liquid in the chamber and driving the samethrough said alternate throats inparallel into the one-half. of themanifold wherein the gas separates from themixture and passes out saidoutlet, the liquid from which gas has been liberated passing peripheryof the; impeller, the maximum angular distance between coperatingadjacent throats connected to different halves of the manifold beingAonly substantially the distance within which the mixture attainsdischarge velocity,

the travel of the priming-liquid in said manifold being at a relativelylowyelocity and in a. long path as compared with its travel in thecasing, said manifold equalizing the supply and gas content of the.priming liquid and serving to stabilize the actionof the pump.

32. A self-priming'centrifugal pump comprising an impeller casing inwhich an impeller is mounted to run for entraining gas and liquid duringpriming and for 'imparting centrifugal force to the mixture to dischargethe same, said vcasing having an axial inlet to which a suction pipe forwater is adapted to be connected, a separator having an outlet at itsupper end for the discharge of y gas during priming and liquid 'dure ingliquid pumping, the impeller casingh'aving a plurality of angularlyspaced discharge ports manifold and which communicate withthe separator,the angular spacing between discharge ports being notsubstantiallygreater than that required to develop full dischargepressure when the pump is supplied with liquid, means to trap suiilcientliquid to establish a working charge for evacuating gas from theimpeller chamber during priming, rotation of the imponer causing thetrapped liquid during priming to be distributed partly inthe impellercasing as a transientmoving pool of liquid entraining gas and passingout of theA discharge ports simultaneously at a plurality of angularlyspaced points to -the separator and partly as a transient moving pool ofliquid in the separatorwhich latter pool gives up vthe en-` trained gasand permits its escape at the said outlet ofthe separator, there being aplurality of auxiliary ports lin the impeller chamber communieating withthe separator and through which liquid from the pool in the separator isreturned to replenish the pool in the impeller chamber, said fauxiliaryports being so disposed with respect to the discharge ports that anexcess of returning liquid at 'one auxiliary port iscarried through agreater angular distance than that in which normal pressure is developedand lmpinges upon another auxiliary port with the eifect of reducinglthereturn ilow whereby the circulation -between said ports isstabilized and maintained in' emcient operation, said pump beingvorganized to discharge liquid throughboth the discharge ports and theauxiliary ports when the inflow of liquid at the inlet increases theamount Vof liquid in the transient pool in the impeller chamber.

33. In a centrifugal pump, an impeller cham-v ber having animpellerlchannel and an impeller.y

therein adapted during-priming to form a mixture of gas andliqiiid andto impart centrifugal force to the mixture to discharge the same, aseparator having an outlet for gas during priming,

a pair of auxiliary throats leading to the impeller channel forreturning liquid from the separator to the impeller channel duringpriming, said Patent No. 2,110,885.

throats being separated angular-1y by'a distance greater than thatrequired to build up normal y CERTIFICATE OE CORRECTION..

stantially greater than that required for building up normal dischargepressure of mixture during priming, whereby the entry of excessivepriming liquid from the auxiliary throat anterior to the dischargethroat in direction of rotation o1' the `impeller will cause liquid tobe carried past the discharge throat and exert a retarding eilect uponthe return flow of the auxiliary throat which is posterior to thedischarge throat. in the direction of rotation of the impeller.

. HARRY E. LA BoUR.

March 15, 1958.

HARRY E. LAy BOUR.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as foilows: Page8,second column, .line 2'?, claim 5, for the article "the" read a; page10A, first Ico1- urnn`-1ine 55, clairn lLL, after. "the" insert said;'page 12, first column,

I line 50, claim 3Q, for "on" read or; and 'that the -said LettersPatentshould be read with these correct-ions therein that the samemay conformto the record of the case in the Patent Office. I

Signed and sealed this'fsd day of May, A.D. 19758.

(Seal)` Henry Van Arsdale, 'Acting Commissioner of Patents a pair ofauxiliary throats leading to the impeller channel for returning liquidfrom the separator to the impeller channel during priming, said PatentNo. 2,110,885.

throats being separated angular-1y by'a distance greater than thatrequired to build up normal y CERTIFICATE OE CORRECTION..

stantially greater than that required for building up normal dischargepressure of mixture during priming, whereby the entry of excessivepriming liquid from the auxiliary throat anterior to the dischargethroat in direction of rotation o1' the `impeller will cause liquid tobe carried past the discharge throat and exert a retarding eilect uponthe return flow of the auxiliary throat which is posterior to thedischarge throat. in the direction of rotation of the impeller.

. HARRY E. LA BoUR.

March 15, 1958.

HARRY E. LAy BOUR.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as foilows: Page8,second column, .line 2'?, claim 5, for the article "the" read a; page10A, first Ico1- urnn`-1ine 55, clairn lLL, after. "the" insert said;'page 12, first column,

I line 50, claim 3Q, for "on" read or; and 'that the -said LettersPatentshould be read with these correct-ions therein that the samemay conformto the record of the case in the Patent Office. I

Signed and sealed this'fsd day of May, A.D. 19758.

(Seal)` Henry Van Arsdale, 'Acting Commissioner of Patents

